Method of thickening and stabilizing latex and product



. Patenlied June 28, 1927.

UNITED STATES 1,634,124 PATENT- OFFICE.

nnnwviv c. TEAGUE, or JACKSON nnronrs, NEW YORK, assreivon TO AMERICAN RUBBER COMPANY, or'sns'r cnmmanen, mssscnusnr'rs, A conrom'rroiv or MASSACHUSETTS.

mnrnon or 'rnicxnnnve AND STABILIZING La'rEx Ann rnonucr.

No Drawing. Original application 'flled June 9, 1924, Serial No. 719,912 Divided and this application filed September 30, 1925. Serial No. 59,595.

This invention relates to a method of I thickening and stabilizing latex and to the product thereof, more particularly for use in coating and extruding.

In the makingof rubberized articles by a coating operation, such as by spreading or dipping, it has been common for many years to use a solution of broken-down or milled rubber in a volatile solventto form the doughs and cements which are applied to the material to be-rubberized to form a coating thereon. For extruding purposes 1t has been necessary to use milled rubber, which has been softened sufiiciently by heat and compounding to possess the desired fluidity and plasticity.

- Owing to the fact that the rubber com pounds used for coating must be varied to some extent in accordance with the particular purpose for which they are designed, and also owin to the fact that the compounds must be dlfierently colored for different purposes, it is necessar to make up a considerable number of di erent-batches in the factory. As such compounds can be most economically made up in large quantities and it is desirable to have a stock of each compound used always on hand for convenience and speed in manufacture, it hasbeen cus-' tomary to mix up such cements and doughs in large batches.

Recently there has been considerable development in the use of rubber latex as such for coating by spreading and dipping. However, as is well known, latex consists of'a sensitive and easily coagulated emulsion of the rubber particles in an aqueous con- 7 tinuous phase, and, owin to its fluidity, it

is unsuitable in its nature condition for certain coating purposes such as 'where it is desired to prevent impregnation of the material bein coated. In addition, by reason of its fluldity it cannot be successfully used with the present types of spreader machines.

pounds become quite sensitive to rubbing or handling and will frequenty coagulate before or during use. Certain chemicals also act to thicken the latex,-but after standing a few hours they render it sensitive and easily coagulated. It has also been possible by the use of certain substances such as glue or gelatine to obtain the desired thickening as well as a certain amount of stability, but

in order to obtain this result it has been necessary to add these substances in such an excessive amount that undesirable properties are imparted to the finished material,

such as lack of flexibility and poor aging properties. Hence, due to these characteristics of latex it has not been practicall possible rior to my invention to pr latex t ickened sufficiently for spreading and uceaextruding and which at the same time has sutficient stability to enable it to be made up in lar e batches and kept for a reason- Still another object is to provide a process for thickening and.stabilizing latex without coagulation, by physical action.

A further object is .to provide a thickened and stabilized uncoagulated latex without the addition thereto of substances. undesirable in themselves or imparting undesirable pro erties to the finished roduct.

For a etailed disclosureof t e nature and the accompanying specification and claims.

The invention consists broadly in the addition to latex of a substance or substances capable of both stabilizing the latex and thickening it to any desired degree, without coagulation thereof and without im arting undesirable properties to the finishe product. The invention also comprises-the product obtained.

This invention is a division of copending objects of theinvention reference is had to application Serial No. 719,015, filed June 9,

The copending application Serial Nb.

' stituents exclusive of the proteins.

- tion 719,015, filed June 9, 1924 sets forth stabilizing and thickening rubber latex by the addition of metallic elements in the form of chemical compounds such as salts of lead,

bismuth, iron, etc. These salts may react to dition, which may be accomplished by adding from to parts of the soap to 100 parts of rubber as latex, but I do not wish to be limited to the maximum given, as very large quantities may be added for certain purposes. While potassium or sodium soaps also have a, thickening and stabilizing actionthe addition of large quantities of thesev is often objectionable by reason of the introduction of the alkali metals, but in the case of ammonium soaps and saponification products there is no such difiiculty of the latex to its purpose the ammonium compound is decomposed with evolution of ammonia gas and leaves the free aliphatic acid (or acid and glycerol as the case. may be) uniformly distributed in. the. rubber compound. Amon the ammonium soaps or saponification pro ucts suitable for use are those with stearic or similar acids of the fatty acid series, .oleic and similaracids, and also the compounds with cocoanut, cotton seed, palm, linseed, and corn oils. 0

An example of such a thickened and stabilized latex compound suitable for spreading onfabrics is the following: 100 parts ru her, (as 60% solids latex), 5 .parts glue,

0.6 part ultramarine blue, 200 parts lithopone, 22 parts ammonium compound of cocoanut oil (dry basis), 1 part zinc oxide, 3 parts sulphur, 0.5 part zinc dimethyl-dithio carbamate.

Another similar example is as follows:

100 parts rubber (as 60% solids latex), 100

parts lithopone, 75 parts barytes, 10 parts glue, 7 parts ammonium stearate (dry basis), 0.5 part ultramarine blue, 1 part zinc oxide, 3 parts sulphur, 0.5 part zinc dimethyl-dithiocarbamate. i

As an example of a physically thickened and stabilized latex compound, using normal latex, the following is given: 100 parts rubber (as normal latex containing about 33% rubber by weight), 35 parts of the ammonium compound of linseed oil by weight), 3 parts sulphur'by weight, 125

as duringthe drying operation after application.

parts whiting by weight, parts glue by.

weight, lpart zinc'oxide-b weight, 0.6 part ultramarine blue by weig t, 0.5 part zinc dimethyl-dithiocarbamate by weight.

-The above compounds may be vulcanized in air in two hours at 212 F. I

In still another form of the. invention 1t has been found that latex may be thickened and stabilized by the addition thereto in suitable proportions of saponin, and the following is given as an example of the use of this thickening and stabilizing agent, us ing 60% concentrated latex. 100 parts rubher by weight (as 60% solids latex), 200

parts lithopone by wei ht, 1 part saponin by weight, 0.5 part Ultramarine blue by weight, 1 part zinc oxide by weight, 3 parts sulphur by weight, 0.5 part zinc dimethyldithiocarbamate.

The above compound may becured, in air in two hours at 212 F.

It will be seen by the use of my invention a thickened and stabilized latex can be pro:

duced by the ,addition thereto ofone or more of the agents mentioned, to provide a latex suitable for such purposes as extruding, spreadingor dipping, without the in-' troduction of any materials which are injurious in themselves or impart .m urious properties to the finished product. Moreover, when it is not-desired to use aconcentrated latex the normal latex may be used instead. I I

In all forms of the invention a. thickening and stabilizing non-protein substance is added to the latex, andin the case of the saponification compounds the compound is decomposed subsequently to its addition and includes a basic substance. In the case of the physically acting saponification compound it is decomposed by the removal of the volatile base when the latex is converted into rubber. In all forms of the invention-a stabilized latex is obtained, and as beforestated by varying the concentration of the later, the quantity and kind of filler, the water, and the quantity and kind of stabilizing and thickening agent any desired degree of thickening may be obtained. Therefore by the use of my invention it is possible to make up latex compounds which will keep for considerable 1 periods of time and the consistency of which may be varied as de sired to adapt them for various purposes such as dipping, spreading, extruding, etc.

My inventlon therefore greatly enlarges the' field of use for rubber latex as such, and at .the same time allows in many cases, such as the spreader machines previously mentioned the use of the same apparatus as was "formerly used with compounds prepared from milled rubber. As even a thick and viscous rubber cement contains a relatively small amount of rubber as compared with latex of very much less viscosity, it

will be seen that b the use of the product of my method a re atively large quantity of rubber can when desired be, applied as a coatin in a single .operation. Moreover the use 0 inflammable andexpensive organic solvents is done away with, and the coat ing obtained from the latex is of superior strength and curing qualities and also is bonded with much greatertenacity to the fibrous or other material to which the coating is applied. Rubberized fabrics and similar materials coated with the product of my invention, or articles formed by extrusion, possess the advantages of great flexibility, good appearance, improved aging qualities and low cost.

While specific examples of the invention have been given it is obvi us that it, is

capable of modification and it is not desired to limit it to the particular examples given or to the specific agents described, otherwise than as defined in the appended claims.

Having thus described my inventidfi, what I claim and desire to protect byLetters Patent is:

1. The process of treating latex which comprises thickening the continuous phase and stabilizing the latex by the addition thereto of a non-metallic saponaceous substance, without substantial modification of the colloidal condition of the rubber hydro-- carbon.

'2. The process of treating latex which comprises thickening the continuous hase and'stabilizing the latex by the ad ition thereto of the saponification product of a volatile base and a substance comprising higher aliphatic acid radicals, without sublatex paste thickened and stabilized v a stantial modification ofth'e colloidal condition of the rubber hydrocarbon.

3. The process of treating latex which parts of rubber.

5 As a new article, an uncoagulated latex paste containing-a saponaceous thickening Y and stabilizing agent.

6. As a new artlcle, an uncoagulated latex paste thickened and stabilized by a volatile base saponi-fication roduct.

7. As a new'artic e, an uncoagulated latex paste thickened and stabilized by an ammonium saponification pro not.

8. As a new article, an uncoagulated latex I paste thickened and stabilized by the volatile-base ,saponification product of a higher aliphatic acid.

9. As a .new article, an uncoagulated latex paste thickened and stabilized by the ammo.- nium saponification product of a higher ali-f phatic acid.

10. As a new article, an uncoaiulated y ammonium stearate.

Signed at New York, count and State of New York, this 24= day of ept.', 1925.

' MERw -N c. TEAGUE. 

